Why coworker is hugging me?

I have a female coworker and we go for a drink after work usually once a week. We are sitting in bar or in park chatting about work, our life,... During these gatherings she started to hug me more and more often. For example when I went to toilet and passing by her she warped her arms around my upper body and saying "I like you so much". I also wrap my arms around her and we stay like this while she starts to stroke my back. Other examples are like we are sitting in park and suddenly she is asking if I can hug her. Or last week I initiated the hug and she hugged me back saying "I'm happy that you are in my life" Girls can you help me to interprete her hugs and what she is saying. As she is in a relationship I assume this is a kind if "best friend" hug. Are there any sign which I can use to understand her intentions or tests I can do?
Why coworker is hugging me?
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